Aurora Over Iceland

An aurora arches over Hveragerdi, Iceland, in a photo recently submitted to National Geographic's My Shot.

Auroras occur when large numbers of charged particles from the sun encounter Earth's magnetic shield. Most of these particles get corralled toward the Poles, where they slam into atmospheric gases such as nitrogen and oxygen.

"Surreal" Desert

Green fields dot a desert in northern Saudi Arabia in an "almost surreal" photograph taken from the International Space Station and released by the NASA Earth Observatory.

Over the past two decades, agriculture has come to the Wadi As-Sirhan Basin thanks to investment of oil-industry revenues by the Saudi government, according to NASA.

The fields are irrigated by water pumped from underground aquifers and distributed carefully via "center pivot" agriculture, which rotates water around a central point in a circular field. This targeted practice cuts down on wasting water, crucial in such an arid region.

In the picture, active fields, seen in both dark greens and browns, are about 0.62 mile (1 kilometer) wide.

Star Trails

The fishers' lights wash out any starlight on the horizon—a common phenomenon worldwide.

Two-thirds of humanity lives under skies polluted with light, and one-fifth can no longer see the Milky Way, according to National Geographic magazine. (Read more about light pollution.)

Published March 12, 2012

Red-Planet Devil

Image courtesy U. Arizona/NASA

A dust devil casts a snake-like shadow over Mars in a "stunning" image released this week by the HiRISE camera team.

Martian dust devils, which can tower five to six miles (eight to ten kilometers) tall, form when summer heat gets the ground warmer than the air above it.

As warm air close to the ground rises, plumes of cooler air fall to replace it, creating vertical circulation. If a gust of wind blows through, it can send the circulating air spinning horizontally, triggering a dust devil.